Ramjets and scramjets (supersonic combustion ramjets) are airbreathing propulsion systems which can propel both manned and unmanned flight vehicles at hypersonic speeds, far beyond the speed range where turbofans and turbojets are no longer viable. Below Mach 3, however, ramjets are inefficient and indeed are incapable of accelerating a vehicle from rest. In order to operate in this flight regime, ramjet/scramjet powered vehicles require a separate low speed propulsion system, which operates either separately from the ramjet or is integrated with it in some fashion to provide a combined cycle propulsion system which can operate in different modes in different flight regimes. A problem with either approach to date has been a large drag penalty associated with increasing the vehicle diameter to accommodate two or more types of propulsion systems and/or the drag resulting from having exposed turbomachinery components in the flow path. Both penalties become unacceptable at very high Mach numbers.